Estimation of inflammation by Doppler ultrasound: quantitative changes after intra-articular treatment in rheumatoid arthritis

Abstract

Objective: To evaluate the use of ultrasound, including quantitative Doppler analysis of synovial vascularisation, before and after intra-articular treatment with glucocorticosteroids in patients with rheumatoid arthritis (RA).

Methods: 51 patients with RA were followed prospectively after an intra-articular glucocorticosteroid injection. Disease modifying antirheumatic drug treatment was kept unchanged and no further injections given in this observation period. At baseline, disease activity was estimated clinically by target join pain on a 100 mm visual analogue scale, on which the target joint was scored 0-3 for swelling and tenderness, and by ultrasound measurements of grey scale pixels, colour Doppler pixels, and the spectral Doppler resistive index (RI) as indicators of synovial swelling and inflammation. After four weeks, the measurements were repeated on the same joint. An observer unaware of the sequence and patient number evaluated the ultrasound images.

Results: At one month follow up after the glucocorticosteroid injection, a marked decrease in the fraction of colour pixels was seen in 41/51 patients (Student's t test p<0.001). Correspondingly, the RI increased indicating a diminished flow to the synovium (Student's t test p<0.01). Both the fraction of colour pixels and the RI values corresponded with the clinical evaluation and with the subjective effect of the treatment. The synovial membrane volume estimated by total amount of pixels showed a significant decrease by 31% after treatment.

Conclusion: Ultrasound-Doppler seems to be a promising tool for the estimation of synovial activity in arthritis. After intra-articular glucocorticosteroid, changes in RI and fraction of colour pixels may both be used as quantitative measurements of the blood flow.

Figure 1

Longitudinal scan of the dorsal side of the right second metatarsophalangeal joint (A) before and (B) four weeks after intra-articular injection with 40 mg methylprednisolone. The synovial tissue is seen as a hypoechoic (dark) mass swelling from the joint. The metacarpal bone is marked "M" and the phalangeal bone "P". The phalangeal bone is subluxated dorsally. In the bottom image the coloured pixels have completely disappeared — a sign of reduced flow in the treated region. The few scattered extrasynovial colour pixels in the bottom image are generated by noise.

Figure 2

Longitudinal scan on the radial side of the left wrist showing the area with most activity (A) before and (B) four weeks after intra-articular injection with 40 mg methylprednisolone. The radial bone (R) is seen at the right side of the image and the metacarpus (MC) at the left. The extensor carpi radialis tendon is marked "T". The synovium has been traced defining the ROI for the calculation of the colour fraction. The trace was made with the help of an extra image (not shown) where the colour had been removed, thereby allowing for definition of the border between synovium and extrasynovial tissue in the areas where it is covered with colour. In both images the Doppler gate (the space between the two horizontal lines on the dotted vertical Doppler line) has been placed over an intrasynovial artery and the resulting spectral curve is shown beneath. The ultrasound unit has traced the spectrum, defined maximum systolic value and end diastolic value, and displayed RI (0.41 and 0.92) in the data boxes. There is a reduction in colour fraction and an increase in peripheral resistance (increase in RI) as signs of reduced flow to the treated region.